vfio: mdev: make a couple of functions and structure vfio_mdev_driver static

The functions vfio_mdev_probe, vfio_mdev_remove and the structure
vfio_mdev_driver are only used in this file, so make them static.

Clean up sparse warnings:
drivers/vfio/mdev/vfio_mdev.c:114:5: warning: no previous prototype
for 'vfio_mdev_probe' [-Wmissing-prototypes]
drivers/vfio/mdev/vfio_mdev.c:121:6: warning: no previous prototype
for 'vfio_mdev_remove' [-Wmissing-prototypes]
Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
Reviewed-by: Quan Xu <quan.xu0@gmail.com>
Reviewed-by: Liu, Yi L <yi.l.liu@intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/mdev/vfio_mdev.c

@@ -111,19 +111,19 @@ static const struct vfio_device_ops vfio_mdev_dev_ops = {
 	.mmap		= vfio_mdev_mmap,
 };
 
-int vfio_mdev_probe(struct device *dev)
+static int vfio_mdev_probe(struct device *dev)
 {
 	struct mdev_device *mdev = to_mdev_device(dev);
 
 	return vfio_add_group_dev(dev, &vfio_mdev_dev_ops, mdev);
 }
 
-void vfio_mdev_remove(struct device *dev)
+static void vfio_mdev_remove(struct device *dev)
 {
 	vfio_del_group_dev(dev);
 }
 
-struct mdev_driver vfio_mdev_driver = {
+static struct mdev_driver vfio_mdev_driver = {
 	.name	= "vfio_mdev",
 	.probe	= vfio_mdev_probe,
 	.remove	= vfio_mdev_remove,